328P - Long-term follow-up of pembrolizumab plus chemotherapy in Chinese patients with metastatic squamous non-small cell lung cancer (NSCLC) from KEYNOTE-407

Background

First-line pembrolizumab (pembro) + paclitaxel and carboplatin (chemo) improved outcomes vs placebo (pbo) + chemo in Chinese patients (pts) with metastatic squamous NSCLC enrolled in the KEYNOTE-407 global and China extension studies, consistent with the global study population. We report long-term outcomes in Chinese pts from these studies.

Methods

Eligible pts in both the phase 3, double-blind KEYNOTE-407 global (NCT02775435) and China extension (NCT03875092) studies were randomized 1:1 to pembro 200 mg or pbo Q3W for up to 35 cycles (∼2 y) + 4 cycles of chemo. Eligible pts in the pbo + chemo group could cross over to pembro monotherapy upon PD. Primary endpoints were OS and PFS per RECIST v1.1 by BICR. No alpha was allocated to this analysis.

Results

125 pts from mainland China were randomized to pembro + chemo (n = 65) or pbo + chemo (n = 60). Median time from randomization to data cutoff (February 23, 2022) was 44.9 (range, 41.9–57.7) mo. 38 pts from the pbo + chemo group crossed over to pembro on-study; 1 additional pt received subsequent anti–PD-(L)1 therapy off-study for an effective crossover rate of 65.0%. The HR for OS was 0.41 (95% CI, 0.27–0.63), with 3-y OS rates of 46.2% for pembro + chemo vs 16.7% for pbo + chemo; additional efficacy data are in the table. Grade 3–5 treatment-related AEs occurred in 53 (81.5%) vs 49 pts (81.7%), with no new grade 5 AEs since previous follow-up. In 19 pts who completed 35 cycles of pembro, ORR was 89.5%, median OS from the time of completing 35 cycles was not reached, and 2-y OS rate after completing 35 cycles (∼4 y after randomization) was 89.2%. Table: 328P

BICR, blinded independent central review; NE, not estimable. “+” indicates no PD by time of last assessment. ^aAssessed per RECIST v1.1 by BICR.

Conclusions

Pembro + chemo maintained improvement in OS and PFS with manageable safety after longer follow-up in Chinese pts in KEYNOTE-407, consistent with the global study population. OS was prolonged in pts who completed 35 cycles of pembro. These data support first-line pembro + chemo as SOC in pts with metastatic squamous NSCLC.

Clinical trial identification

NCT02775435, NCT03875092.

Editorial acknowledgement

Medical writing and editorial assistance was provided by Christabel Wilson, MSc, of ICON plc (Blue Bell, PA, USA). This assistance was funded by Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, USA.

Legal entity responsible for the study

Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, USA.

Funding

Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, USA.

Disclosure

L. Zhang, J. Hu, D. Wang, C.P. Hu, J. Zhou, L. Wu, L. Cao, J. Liu H. Zhang, H. Sun, Z. Wang, H. Gao: Financial Interests, Institutional, Funding: Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, USA. Y. Sun: Financial Interests, Personal, Full or part-time Employment: MSD China. X. Hu, E. Jensen, P.O. Schwarzenberger: Financial Interests, Personal, Full or part-time Employment: Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, USA; Financial Interests, Personal, Stocks/Shares: Merck & Co., Inc., Rahway, NJ, USA. L. Paz-Ares: Financial Interests, Personal, Other, honoraria to self/spouse: Adacap, Amgen, AstraZeneca, Bayer, Blueprint Medicines, BMS, Boehringer Ingelheim, Celgene, Incyte, Ipsen, Lilly, Merck, MSD, Novartis, PharmaMar, Pfizer, Roche, Sanofi, Servier, and Sysmex; Financial Interests, Personal, Other, board member: Genómica and Altum Sequencing; Financial Interests, Institutional, Research Grant: AstraZeneca, BMS, MSD, and Pfizer; Financial Interests, Institutional, Funding: Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, USA. All other authors have declared no conflicts of interest.